In the next project year, we plan to continue several ongoing lines of research, including: (1) efforts to obtain and analyze new mutations and new combinations of mutations affecting cell division and cell patterning; (2) a careful analysis of the phenotype of what is probably our most important single mutation, psml, including its expression both when it is in doubly homozygous combinations with other genes affecting cell division, shape, and pattern; (3) a continued analysis of the spatial determination of positioning of the contractile vacuole pore, both in lines with inverted ciliary meridians and in mutants with varying degrees of division blockage and varying fission sites; (4) continued study of ciliary meridian inversions, including a genetic analysis to demonstrate the (presumed) non-genic basis for their origin and perpetuation; (5) a concerted attempt to analyze the control of the positioning and internal asymmetry of the developing oral apparatus, mainly by attempting to obtain an inversion of the particular ciliary meridian along which the new oral apparatus develops; (6) continued study of the times of expression of mutations through single-cell temperature shifts, concentrating on psml. BIBLIOGRAPHIC REFERENCES: Doerder, F.P., J. Frankel, L.M. Jenkins, and L.E. DeBault 1975. Form and pattern in ciliated protozoa: Analysis of a genic mutant with altered cell shape in Tetrahymena pyriformis. J. Exp. Zool. 192, 237-258. Frankel, J., Doerder, F.P., Jenkins, L.M., and Nelson, E.M. 1976. Mutations affecting cell division in Tetrahymena pyriformis. I. Selection and Genetic Analysis. Genetics, In Press.